The field of the disclosure relates generally to components having an outer wall of a preselected thickness, and more particularly to forming such components using a jacketed core.
Some components require an outer wall to be formed with a preselected thickness, for example, in order to perform an intended function. For example, but not by way of limitation, some components, such as hot gas path components of gas turbines, are subjected to high temperatures. At least some such components have internal voids defined therein, such as but not limited to a network of plenums and passages, to receive a flow of a cooling fluid adjacent the outer wall, and an efficacy of the cooling provided is related to the thickness of the outer wall.
At least some known components having a preselected outer wall thickness are formed in a mold, with a core of ceramic material positioned within the mold cavity. A molten metal alloy is introduced around the ceramic core and cooled to form the component, and the outer wall of the component is defined between the ceramic core and an interior wall of the mold cavity. However, an ability to produce a consistent preselected outer wall thickness of the cast component depends on an ability to precisely position the core relative to the mold to define the cavity space between the core and the mold. For example, the core is positioned with respect to the mold cavity by a plurality of platinum locating pins. Such precise and consistent positioning, for example using the plurality of pins, is complex and labor-intensive in at least some cases, and leads to a reduced yield rate for successfully cast components, in particular for, but not limited to, cases in which a preselected outer wall thickness of the component is relatively thin. In addition, in at least some cases, the core and mold shift, shrink, and/or twist with respect to each other during the final firing before the casting pour, thereby altering the initial cavity space dimensions between the core and the mold and, consequently, the thickness of the outer wall of the cast component. Moreover, at least some known ceramic cores are fragile, resulting in cores that are difficult and expensive to produce and handle without damage during the complex and labor-intensive process.
Alternatively or additionally, at least some known components having a preselected outer wall thickness are formed by drilling and/or otherwise machining the component to obtain the outer wall thickness, such as, but not limited to, using an electrochemical machining process. However, at least some such machining processes are relatively time-consuming and expensive. Moreover, at least some such machining processes cannot produce an outer wall having the preselected thickness, shape, and/or curvature required for certain component designs.